West Pacific/2015/09W/Archive/20
Public advisory TROPICAL STORM CHAN-HOM PUBLIC ADVISORY NUMBER 20 WIKI-HURRICANES FORECASTING CENTER 6:00 AM JST SUN JUL 05 2015 ...CHAN-HOM BECOMING BETTER ORGANIZED AS IT MOVES THROUGH THE MARIANA ISLANDS... SUMMARY OF 6:00 AM JST...21:00 UTC...INFORMATION ------------------------------------------------------------------- LOCATION...13.9N 145.4E CENTER POSITION CONFIDENCE: HIGH ABOUT 55 MI...90 KM NNE OF HAGATNA, GUAM MAXIMUM SUSTAINED WINDS...55 KT...65 MPH...100 KM/H MINIMUM BAROMETRIC PRESSURE...991 MB...29.27 INCHES PRESENT MOVEMENT...WNW AT 6 KT...7 MPH...11 KM/H DISCUSSION AND 48-HOUR OUTLOOK --------------------------------------------- At 6:00 am JST, the center of Tropical Storm Chan-hom was situated near 13.9N 145.4E, or about 55 miles (90 km) north-northeast of Hagatna, Guam. Maximum sustained winds were 55 knots (65 mph, 100 km/h), with higher gusts. The minimum barometric pressure was 991 millibars (hPa; 29.27 inHg), and the cyclone was tracking west-northwest at 6 knots (7 mph, 11 km/h). Environmental conditions are expected to favor steady to rapid intensification throughout the forecast period, and Chan-hom is likely to become an exceptionally powerful typhoon in the West Pacific over the coming days. NEXT ADVISORY ------------------- Next complete advisory at 12:00 am JST. $$ Forecaster TAWX14 Discussion TROPICAL STORM CHAN-HOM PUBLIC DISCUSSION NUMBER 20 WIKI-HURRICANES FORECASTING CENTER 6:00 AM JST SUN JUL 05 2015 Tropical Storm Chan-hom has continued to organize this morning. Satellite animations show a well-formed cyclone, with a uniform central dense overcast and prominent spiral banding to the south. Long-range radar out of Guam suggests that the system is in the process of developing an inner core, supported by the presence of numerous overshooting tops on conventional satellite. Although recent satellite intensity estimates from SAB and JTWC were T3.0/45kt, the estimate from UW-CIMSS ADT has risen to T3.8/61kt. Based on the improving structure, the initial intensity has been edged upward to 55kt. The environment for Chan-hom is expected to be exceptionally conducive for steady to rapid intensification. Wind shear has fallen to a low 5 to 10 knots, and outflow channels both poleward and equatorward are becoming evident. After traversing 27-28C sea surface temperatures over the past few days, Chan-hom is entering a region characterized by ocean temperatures over 30C and more than adequate ocean heat content. Finally, water vapor animations indicate that the cyclone remains embedded within a region of high mid-level moisture. Forecasts from global models continue to be bullish, with the ECMWF indicating a minimum pressure near 940mb in 5 days and the GFS indicating a minimum pressure near 925mb at the same time. The HWRF model is even more incredible, outputting 850mb winds of 217 kt at 850mb along with a minimum barometric pressure of 897mb! It should be noted, however, that neither global nor hurricane models can forecast the inner structural changes that take place within cyclones. Nevertheless, it is clear that Chan-hom will become a very powerful typhoon within the West Pacific over the next few days. Chan-hom has continued on its steady west-northwest track this morning. The system is being influenced by a 594dm mid-level ridge across the northern West Pacific, and this steering motion is expected to continue throughout the forecast period. Both the GFS and ECMWF indicate a stronger anticyclone today versus yesterday, and so the track forecast in the extended range has shifted southward substantially. However, both of the models differ on the exact strength of the ridge, with the GFS tracking Chan-hom farther south than its counterpart. Given the run-to-run changes, the current track forecast is one of low confidence, and residents across both the Japanese Islands and China are urged to closely monitor the progress of Chan-hom. INIT 04/2100Z 13.9N 145.4E 55 KT 65 MPH 12H 05/0600Z 14.4N 144.3E 65 KT 75 MPH 24H 05/1800Z 15.2N 144.4E 75 KT 85 MPH 36H 06/0600Z 16.2N 141.1E 85 KT 100 MPH 48H 06/1800Z 17.4N 139.2E 100 KT 115 MPH 72H 07/1800Z 20.4N 134.8E 125 KT 145 MPH 96H 08/1800Z 23.7N 130.2E 140 KT 160 MPH 120H 09/1800Z 26.9N 125.5E 140 KT 160 MPH $$ Forecaster TAWX14